And I'm Audie Cornish. Two American missionaries who caught the Ebola virus while working in Liberia have been released from the hospital. Emory University Hospital in Atlanta announced today that Doctor Kent Brantly and Nancy Writebol had recovered enough to be safely discharged. NPR's Rob Stein joins us with the latest on their condition. And Rob remind us how these two Americans got infected and how they ended up in Atlanta.

ROB STEIN, BYLINE: Well, Doctor Brantly was there treating Ebola patients as part of a team of U.S. missionaries who were in Liberia with an aid group called Samaritan's Purse. And Nancy Writebol was there with another Christian missionary group known as SIM International. She was working to disinfect healthcare workers as they went in and out of this clinic. And they both felt deathly ill after getting the virus themselves. And it's unclear still at this point exactly how they got infected. But eventually they were airlifted to Emory making them the only Ebola patients brought this country to be treated.

CORNISH: So what more do we know about how they're doing?

STEIN: Nancy Writebol was discharged very quietly on Tuesday and hasn't appeared in public since. But SIM International released a statement from her husband saying that she was able to walk out of the hospital, but she was still suffering lingering effects from her fight with the virus and she was still significantly weakened. She's 59 and so older than Doctor Brantly who's 33. He appeared at a news conference with his doctors. Let's listen to a little of what he said today.

(SOUNDBITE OF NEWS CONFERENCE)

KENT BRANTLY: Today is a miraculous day. I am thrilled to be alive, to be well and to be reunited with my family.

STEIN: After making the statement Doctor Brantley made a point of hugging every single member of the hospital staff who was in the room.

CORNISH: Which is of course remarkable because of the concerns about bringing these patients to the United States, right? I mean, people thought that they could be posing a public health concern. What did doctors say about that?

STEIN: Doctor Bruce Ribner who led the team that treated both of these patients repeated several times that bringing them in the first place and releasing them now posed absolutely no danger to the public. They tested these patients repeatedly and there was no evidence of the virus in their bodies. He also said that there is evidence from previous outbreaks in Africa that patients are no longer contagious after they've reached this point in their recovery. Here's how he explained that.

(SOUNDBITE OF NEWS CONFERENCE)

BRUCE RIBNER: The standard World Health Organization and CDC guidelines that have been used in the Third World have been absence of virus in the blood and patient symptomatically improved for at least two to three days.

CORNISH: You know, Rob, another reason this case has gotten so much attention is because it's the first of only a handful of patients to get an experimental drug, right? I mean, what did the doctors say about whether that played any role in their recovery?

STEIN: Both of these patients received this drug known as ZMAP. I think a lot of people have heard about it at this point. It's a combination of antibodies designed to fight the virus. And Samaritan's Purse says Doctor Brantly also got a blood transfusion from a 14-year-old boy who he helped recover from Ebola. Dr. Ribner said, that basically doctors have no idea how any of this might have affected them and that means they have no ideal whether it helped, whether it did nothing or maybe whether it could have hindered the recovery in some way. There's just no way to know from just two patients.

CORNISH: But did they say that they learned some things from treating these patients - things that could be useful for treating future patients?

STEIN: They did. They said they learned some very valuable things that they plan to pass on to doctors in Africa who are treating patients now. And they said that one of the things they learned is that patients can experience a very serious imbalance in what's called electrolytes. This is things like calcium and potassium that can get out of whack. And that can cause some very serious complications. And what they're saying is that in places where there's no easy way to test for that, which is in a lot of places in Africa, that doctors can then simply give patients infusions of electrolytes to get balance back in the right place. In addition they found that these patients experience severe nutritional deficiencies and giving them high-protein liquid, nutritional supplements rich in vitamins might be helpful.

CORNISH: Rob, thanks so much for talking with us.

STEIN: Nice to be here.

CORNISH: NPR science correspondent and editor Rob Stein on the release today of two U.S. Ebola patients from an Atlanta hospital. Transcript provided by NPR, Copyright NPR.